Part 4: Adult Basic Life Support IV-2 compressions interrupted by pauses for ventilation). Instead, more than 10 seconds to check for a pulse( Class Ila). If a the compressing rescuer should give continuous chest com- pulse is not definitely felt within 10 seconds, proceed with pressions at a rate of 100 per minute without pauses for chest compressions(see below ) ventilation. The rescuer delivering ventilation provides8 to 10 breaths per minute. The 2 rescuers should change com- Rescue Breathing Without Chest Compressions pressor and ventilator roles approximately every 2 minutes to (for Healthcare Providers Only-Box 5A) prevent compressor fatigue and deterioration in quality and If an adult victim with spontaneous circulation (ie, palpable rate of chest compressions. When multiple rescuers are pulses)requires support of ventilation, give rescue breaths at present, they should rotate the compressor role about every 2 a rate of 10 to 12 breaths per minute, or about I breath every 5 to 6 seconds(Class IIb). Each breath should be given over Rescuers should avoid excessive ventilation by giving the I second regardless of whether an advanced airway is in recommended breaths per minute and limiting tidal volume to place. Each breath should cause visible chest rise. achieve chest rise(Class Ila). 15 A translational research study During delivery of rescue breaths, reassess the pulse showed that delivery of >12 breaths per minute during CPR approximately every 2 minutes( Class lla), but spend no more leads to increased intrathoracic pressure, impeding venous retum than 10 seconds de to the heart during chest compressions. 5 Reduced venous return leads to diminished cardiac output during chest compres- Chest Compressions(Box 6) sions and decreased coronary and cerebral perfusion. 50, I5I It is est compressions consist of rhythmic applications of pres- critically important that rescuers maintain a ventilation rate of8 sure over the lower half of the sternum. These compressions to 10 breaths per minute during CPR and avoid excessive reate blood flow by increasing intrathoracic pressure and directly compressing the heart. Although properly performed chest compressions can produce systolic arterial pressure Automatic Transport Ventilators and Manually Triggered, peaks of 60 to 80 mm Hg, diastolic pressure is low l18 and Flow-Limited Resuscitators mean arterial pressure in the carotid artery seldom exceeds Automatic transport ventilators(ATVs)are useful for venti- 40 mm Hg. 18 lation of adult patients with a pulse who have an advanced Blood flow generated by chest compressions delivers a airway in place, both in and out of the hospital(Class lla). For small but critical amount of oxygen and substrate to the brain the adult cardiac arrest patient who does not have an and myocardium In victims of VF SCA, chest compressions advanced airway in place, the ATV may be useful if tidal increase the likelihood that a shock (ie, attempted defibrilla volumes are delivered by a flow-controlled, time-cycled tion)will be successful. Chest compressions are especially ventilator without positive end-expiratory pressure (PEEP) important if the first shock is delivered >4 minutes after Manually triggered, oxygen-powered, flow-limited collapse. 36, citator may be considered for mask ventilation of the pater Much of the information about the physiology of chest who does not have an advanced airway in place during CPR impressions and the effect of varying compression rates, For further information about these devices see part 6 con npression-ventilation ratios, and duty cycles(percent of Cricoid Pressure time the chest is compressed versus time allowed for chest Pressure applied to the victims cricoid cartilage pushes the recoil)is derived from animal models. Researchers at the trachea posteriorly, compresses the esophagus against the 2005 Consensus Conference. 157 however. reached several cervical vertebrae, and can prevent gastric inflation and conclusions about chest compressions reduce the risk of regurgitation and aspiration. 152-153 Appli- cation of cricoid pressure usually requires a third rescuer, one L.“ Effective ons are essential for providing blood flow who is not responsible for chest compressions or ventilations CPR( Class D) Cricoid pressure should be used only if the victim is deeply 2. To give"effective"chest compressions, "push hard and push fast. "Compress the adult chest at a rate of about 100 unconscious (ie, has no cough or gag reflex) ion depth of 1 2 to 2 inches(approximately 4 to 5 cm). Allow the chest to Pulse Check(for Healthcare Providers)(Box 5) recoil completely after each compression, and allow ap- Lay rescuers fail to recognize the absence of a pulse in 10% ximately equal compression and relaxation times of pulseless victims(poor sensitivity for cardiac arrest) and 3. Minimize interruptions in chest compressions fail to detect a pulse in 40% of victims with a pulse (poor 4. Further studies are needed to define the best method for specificity). In the ECC Guidelines 2000117 the pulse check coordinating ventilations and chest compressions and to was deleted from training for lay rescuers and deemphasized identify the best compression-ventilation ratio in terms of in training for healthcare providers. There is no evidence, survival and neurologic outcome. however, that checking for breathing, coughing, or movement Technique is superior for detection of circulation. 54 For ease of training, To maximize the effectiveness of compressions, the victim the lay rescuer will be taught to assume that cardiac arrest is should lie supine on a hard surface (eg, backboard or present if the unresponsive victim is not breathing floor), 58 with the rescuer kneeling beside the victims tho- Healthcare providers also may take too long to check for a rax. 159 The safety and efficacy of over-the-head CPR(OTH- pulsel09,155 and have difficulty determining if a pulse is CPR) for lone rescuers and 2-person straddle CPR are resent or absent. The healthcare provider should take no unknown, but these techniques may be advantageous incompressions interrupted by pauses for ventilation). Instead, the compressing rescuer should give continuous chest com￾pressions at a rate of 100 per minute without pauses for ventilation. The rescuer delivering ventilation provides 8 to 10 breaths per minute. The 2 rescuers should change com￾pressor and ventilator roles approximately every 2 minutes to prevent compressor fatigue and deterioration in quality and rate of chest compressions. When multiple rescuers are present, they should rotate the compressor role about every 2 minutes. Rescuers should avoid excessive ventilation by giving the recommended breaths per minute and limiting tidal volume to achieve chest rise (Class IIa).115 A translational research study showed that delivery of
12 breaths per minute during CPR leads to increased intrathoracic pressure, impeding venous return to the heart during chest compressions.115 Reduced venous return leads to diminished cardiac output during chest compres￾sions and decreased coronary and cerebral perfusion.150,151 It is critically important that rescuers maintain a ventilation rate of 8 to 10 breaths per minute during CPR and avoid excessive ventilation.115,150 Automatic Transport Ventilators and Manually Triggered, Flow-Limited Resuscitators Automatic transport ventilators (ATVs) are useful for venti￾lation of adult patients with a pulse who have an advanced airway in place, both in and out of the hospital (Class IIa). For the adult cardiac arrest patient who does not have an advanced airway in place, the ATV may be useful if tidal volumes are delivered by a flow-controlled, time-cycled ventilator without positive end-expiratory pressure (PEEP). Manually triggered, oxygen-powered, flow-limited resus￾citators may be considered for mask ventilation of the patient who does not have an advanced airway in place during CPR. For further information about these devices see Part 6. Cricoid Pressure Pressure applied to the victim’s cricoid cartilage pushes the trachea posteriorly, compresses the esophagus against the cervical vertebrae, and can prevent gastric inflation and reduce the risk of regurgitation and aspiration.152,153 Appli￾cation of cricoid pressure usually requires a third rescuer, one who is not responsible for chest compressions or ventilations. Cricoid pressure should be used only if the victim is deeply unconscious (ie, has no cough or gag reflex). Pulse Check (for Healthcare Providers) (Box 5) Lay rescuers fail to recognize the absence of a pulse in 10% of pulseless victims (poor sensitivity for cardiac arrest) and fail to detect a pulse in 40% of victims with a pulse (poor specificity). In the ECC Guidelines 2000117 the pulse check was deleted from training for lay rescuers and deemphasized in training for healthcare providers. There is no evidence, however, that checking for breathing, coughing, or movement is superior for detection of circulation.154 For ease of training, the lay rescuer will be taught to assume that cardiac arrest is present if the unresponsive victim is not breathing. Healthcare providers also may take too long to check for a pulse109,155 and have difficulty determining if a pulse is present or absent. The healthcare provider should take no more than 10 seconds to check for a pulse (Class IIa). If a pulse is not definitely felt within 10 seconds, proceed with chest compressions (see below). Rescue Breathing Without Chest Compressions (for Healthcare Providers Only—Box 5A) If an adult victim with spontaneous circulation (ie, palpable pulses) requires support of ventilation, give rescue breaths at a rate of 10 to 12 breaths per minute, or about 1 breath every 5 to 6 seconds (Class IIb). Each breath should be given over 1 second regardless of whether an advanced airway is in place. Each breath should cause visible chest rise. During delivery of rescue breaths, reassess the pulse approximately every 2 minutes (Class IIa), but spend no more than 10 seconds doing so. Chest Compressions (Box 6) Chest compressions consist of rhythmic applications of pres￾sure over the lower half of the sternum. These compressions create blood flow by increasing intrathoracic pressure and directly compressing the heart. Although properly performed chest compressions can produce systolic arterial pressure peaks of 60 to 80 mm Hg, diastolic pressure is low118 and mean arterial pressure in the carotid artery seldom exceeds 40 mm Hg.118 Blood flow generated by chest compressions delivers a small but critical amount of oxygen and substrate to the brain and myocardium. In victims of VF SCA, chest compressions increase the likelihood that a shock (ie, attempted defibrilla￾tion) will be successful. Chest compressions are especially important if the first shock is delivered
4 minutes after collapse.36,37,156 Much of the information about the physiology of chest compressions and the effect of varying compression rates, compression-ventilation ratios, and duty cycles (percent of time the chest is compressed versus time allowed for chest recoil) is derived from animal models. Researchers at the 2005 Consensus Conference,157 however, reached several conclusions about chest compressions: 1. “Effective” chest compressions are essential for providing blood flow during CPR (Class I). 2. To give “effective” chest compressions, “push hard and push fast.” Compress the adult chest at a rate of about 100 compressions per minute, with a compression depth of 11⁄2 to 2 inches (approximately 4 to 5 cm). Allow the chest to recoil completely after each compression, and allow ap￾proximately equal compression and relaxation times. 3. Minimize interruptions in chest compressions. 4. Further studies are needed to define the best method for coordinating ventilations and chest compressions and to identify the best compression-ventilation ratio in terms of survival and neurologic outcome. Technique To maximize the effectiveness of compressions, the victim should lie supine on a hard surface (eg, backboard or floor),158 with the rescuer kneeling beside the victim’s tho￾rax.159 The safety and efficacy of over-the-head CPR (OTH￾CPR) for lone rescuers and 2-person straddle CPR are unknown, but these techniques may be advantageous in Part 4: Adult Basic Life Support IV-25